1. Field of Invention
This invention applies to the field of DC to DC power conversion and in particular to converters required to provide high power density.
2. Prior Art
A vast variety of topologies have been invented over the years with the purpose of improving power density of power converters. Some of these topologies provide means to reduce or to eliminate switching losses in order to allow increased frequency of operation, increased efficiency, reduced size and weight. Typical of this approach is the technique disclosed in U.S. Pat. No. 4,415,959, issued to P. Vinciarelli, for "Forward Converter Switching at Zero Current" which reduces the size of the energy storage components.
Another approach is disclosed by U.S. Pat. No. 4,618,919, issued to Hubert C. Martin, Jr., for "Topology for Miniature Power Supply with Low Voltage and Low Ripple Requirements". This patent combines two single ended (flyback) converters to increase effective ripple frequency and reduce the size of energy storage components.
Another approach is to maximize the energy of switching devices and the transformer in order to improve the power transfer characteristics of the converter as indicated in U.S. Pat. No. 4,441,146 issued to P. Vinciarelli for "Optimal resetting of the transformer's core in single ended forward converters" and in U.S. Pat. No. 4,809,148 issued to Barn for "Full-fluxed, single ended DC converter".
Finally, in an article published in the PCIM magazine, January 1991, p. 8, "New PWM Topology features zero- voltage switching and constant switching frequency", and also disclosed in U.S. Pat. No. 4,959,764, John A. Bassett proposes a topology that offers both the improved utilization of components and lossless switching, thereby allowing efficient operation at high frequency. While each of the above disclosures addresses some facets of the power conversion issue, none provides an approach achieving all of the advantages discussed above.